Hydrocyanation catalyst systems, particularly pertaining to the hydrocyanation of olefins, are known in the art. For example, systems useful for the hydrocyanation of butadiene to form pentenenitrile (PN) and in the subsequent hydrocyanation of pentenenitrile (PN) to form adiponitrile (AND), are known in the commercially important nylon synthesis field.
The hydrocyanation of olefins using transition metal complexes with monodentate phosphite ligand is documented in the prior art. See for example; U.S. Pat. Nos. 3,496,215, 3,631,191, 3,655,723 and 3,766,237, and Tolman, C. A.; McKinney, R. J.; Seidel, W. C.; Druliner, J. D.; and Stevens, W. R.; Advances in Catalysis, 33, 1, 1985.
The hydrocyanation of activated olefins such as with conjugated olefins (e.g., butadiene and styrene) and strained olefins (e.g., norbornene) proceeds without the use of a Lewis acid promoter, while hydrocyanation of unactivated olefins such as 1-octene and 3-pentenenitrile requires the use of a Lewis acid promoter. Teachings regarding the use of a promoter in the hydrocyanation reaction appear, for example, in U.S. Pat. No. 3,496,217. This patent discloses an improvement in hydrocyanation using a promoter selected from a large number of metal cation compounds with a variety of anions as catalyst promoters.
U.S. 3,496,218 discloses a nickel hydrocyanation catalyst promoted with various boron-containing compounds, including triphenylboron and alkali metal borohydrides. U.S. Pat. No. 4,774,353 discloses a process for the preparation of dinitriles, including ADN, from unsaturated nitriles, including PN, in the presence of a zero-valent nickel catalyst and a triorganotin catalyst promoter. U.S. Pat. No. 4,874,884 discloses a process for producing ADN by the zero-valent nickel catalyzed hydrocyanation of pentenenitriles in the presence of a synergistic combination of promoters selected in accordance with the reaction kinetics of the ADN synthesis.
Bidentate phosphite ligands similar to those used in the present invention for the hydrocyanation of monoolefins have been shown to be useful ligands in the hydrocyanation of activated olefins. See, for example: Baker, M. J., and Pringle, P. G.; J. Chem. Soc., Chem. Commun., 1292, 1991; Baker, M. J.; Harrison, K. N.; Orpen, A. G.; Pringle, P. G.; and Shaw, G.; J. Chem. Soc.; Chem. Commun., 803, 1991, Union Carbide, WO 93,03839. Also, similar ligands have been disclosed with rhodium in the hydroformylation of functionalized olefins; Cuny et al., J. Am. Chem. Soc. 1993, 115, 2066.
The present invention provides novel processes and catalyst precursor compositions which are rapid, selective, efficient and stable in the hydrocyanation of monoolefins. Other objects and advantages of the present invention will become apparent to those skilled in the art upon reference to the detailed description which hereinafter follows.